The present invention relates to a gas flow controller specifically driven by electrical means and used in controlling the burning quantity of fuel gas supplied to a cooking machine, a heater or a hot water supplier.
A gas flow controller is used in various applications which requires a control of the burning quantity of gas in accordance with the conditions of an object to be burnt. Recently, such a control is conducted through regulation of an electric quantity. A most simple but frequently used controller is a controller constructed of electromagnetic valves shown in FIG. 1. The controller comprises a plurality of electromagnetic valves 3 mounted in parallel to each other at a plurality of gas passageways 2 to a burner 1, and a plurality of orifices 4 each having a different diameter and connected in series to a corresponding electromagnetic valve. A maximum burning quantity is attained when all the electromagnetic valves 3 are opened, whereas a minimum burning quantity is attained when only the electromagnetic valve 3 having a smallest orifice 4 diameter is opened. The gas burning quantity can be stepwise changed between the maximum and minimum burning quantity in accordance with a combination of the plurality of electromagnetic valves 3. Obviously, a combustion stops when all the electromagnetic valves are closed.
An alternative example of a controller which successively changes a burning quantity is shown in FIG. 2. A valve opening 8 and a valve 9 are provided along a gas passageway 5 between an inlet 6 and an outlet 7. The valve is supported at its end on a diaphragm 10 to which a permanent magnet 11 is attached. An electromagnetic 14 consisting of a magnetic iron core 12 and an exciting coil 13 is mounted facing the permanent magnet 11. The gas flow entering to the gas passageway 5 is regulated in accordance with the quantity of electricity supplied to the exciting coil 13. Particularly, when a current flows through the exciting coil 13 such that the polarity of the magnetic core 12 causes a repulsion force to be generated against the permanent magnet 11, the valve 9 moves away from the valve opening 8 to allow the gas to flow. The gas pressure at the outlet 7 is determined by the repulsion force and the effective pressure receiving area of the diaphragm 10 so that the gas pressure applied to the burner at the downstream can be controlled in accordance with the quantity of electricity supplied to the exciting coil 13. Contrary to the above, the permanent magnet 11 attracts the magnetic iron core 12 when a current is not fed to the exciting coil 13. Therefore, if a soft elastic member 15 is provided on the surface of the valve 9, the gas flow can be stopped (see for example Japanese Unexamined Utility Model Publication No. 55-49137).
A further example of a controller with a manual cock which can multi-stepwise regulate a burning quantity is shown in FIGS. 3 to 10. In a gas cock main body 18 having a gas inlet 16 and a gas outlet 17, a closing member 21 is rotatably mounted which has a gas opening 19 at its side wall cooperating with the gas inlet 16 and a guide hole 20 formed in the axial direction of the closing member 21 and communicating with the gas opening 19. A first passageway 22 of a small reduction ratio, a second passageway 23 of a middle reduction ratio and a third passageway 24 with a large reduction ratio are formed in the cock main body 18 to communicate with the gas outlet 17 at their ends at the downstream. The ends of the first and second passageways 22 and 23 open at the upstream to the guide hole 20 via gas openings 25 and 26 formed at the side wall of the closing member 21, while the end of the third passageway 24 opens at its upstream to a chamber 27 at the bottom surface of the cock main body 18 which chamber communicates with the guide hole 20. Thus, the gas flow can be changed to three different steps (see for example Japanese Unexamined Utility Model Publication No. 59-21324).
In the above example, if a control shaft 28 is depressed, a pilot valve 29 opens. The guide hole 20 communicates with a pilot gas outlet 31 via the valve 29 and a gas opening 30 formed in the side wall at the downstream. A piezoelectric ignition device 32 cooperative with the control shaft 28 and a rotation display device 33 for visually recognizing a rotary position are mounted at the base of the control shaft 28.
The above conventional flow controllers have to be entirely been found not satisfactory. Particularly, the example shown in FIG. 1 requires a number of electromagnetic valves, resulting in a large size controller which is not suitable for mounting in other application apparatus. Further, since the total quantity of electricity becomes high when all the electromagnetic valves are opened, generation of heat affects the associated apparatus and a large and expensive power supply circuit is required. The controller shown in FIG. 2 has a limit in a ratio of a maximum flow to a minimum flow, i.e., a reduction ratio. A clearance at the valve opening 8 becomes extremely small with a part of the opening 8 being in contact with the valve 9, so that the reproducibility of a relationship between the electricity quantity and the supply gas pressure becomes unstable. Therefore, this controller is not suitable for practical application where an optional reduction ratio is needed. Further, the relationship between the electricity quantity and the gas pressure differs for each manufacture due to manufacture tolerance of permanent magnets and magnetic circuits, so that it has been necessary to set current values for maximum and minimum burning quantities at the time of manufacturing. In addition, since the pressure applied to the valve by the attraction force of the permanent magnet while a current is not fed is weak, a reliable airtight condition cannot be expected.
In the example shown in FIGS. 3 to 10, gas is introduced from the gas opening 19 formed at the side wall of the closing member 21, guided via the internal guide hole 20 to either the passageway 22, 23 at the side wall of the closing member 21 or the passageway 24 communicating with the bottom chamber 27 of the closing member 21, subjected to regulation of three, i.e., small, middle and large reduction ratios, and outputted from the gas outlet 17. Therefore, if the gas flow is required to be multi-stepwise regulated, for example, in five steps or six steps, it becomes necessary to use a large size closing member 21 with an increased diameter. Because of this reason or some other reasons, the controller of this example is not suitable for mass production and has too large an outer dimension to mount and assemble it in home appliances.
In FIGS. 6 to 9, the upper portions show sectional views of the member 21 taken along the line X--X, the middle portions show the sectional views taken along the line Y--Y, the lower portions show the sectional views taken along the line Z--Z, respectively of FIG. 4.